Chapter 8: Earthquakes and Earth's Interior Flashcards
(43 cards)
What is an Earthquake?
ground shaking caused by a rapid release of energy inside the Earth due to tectonic stresses that cause rocks to break suddenly along fault lines
When a fault slips, energy is released and travels outwards causing what?
A seismic wave
EX: waves created when a pebble is dropped into a pond
What is a a Focus of a seismic wave?
The point inside the Earth on fault where earthquakes are originated
What is a Epicenter of a seismic wave?
The point on the Earth’s surface that is directly above the Focus
Types of Earthquake faults
Normal fault (downward)
Reverse fault (upward)
Left-lateral fault
Right-lateral fault
Foot wall &
Hanging wall
Foot wall– the part of the fault you can climb up.
Hanging wall– the part of the fault that looks like it is “hooked” onto the foot wall.
Earthquake in Port-au-Prince, Haiti
a) Magnitude of 7.0
b) killing 24% of population
c) left-lateral strike-slip fault
d) 4:53 pm, Jan. 12, 2010
e) 52 aftershocks
Great San Francisco Earthquake
a) 7. 8 magnitude
b) April 18, 1906
c) problem– fires breaking out from candles/stoves knocking ove
What geology professor headed the commission at UC- Berkeley?
Andrew Lawson
Elastic Rebound Theory
bent rocks straightened with a sudden snap.
EX: rubber band or a a yard stick being bent or stretched.
(San Andreas Fault of 1906)
Causes of Earthquakes:
Stress
the force imposed on a rock
Causes of Earthquakes:
Strain
a change in the shape of a rock, in response to the stress it is undergoing.
Rocks under low stress cause what?
Deform elastically under low stress.
Revert to former shape when stress is removed
Rocks under high stress cause what?
Deform plastically under high stress.
Permanently change shape of flow
What is a fault?
fractures in the crust along which rocks on one side move past rocks on the either side; this movement can be either vertical or horizontal.
Faults are mostly located where?
along the plate boundaries.
Types of Earthquake waves
Body waves
p-wave s-wave
Surface waves
l-wave r-wave
What is a body wave and it’s secondary waves?
They travel through the body of the earth.
Primary wave- compressional motion (push-pull) feels like a sudden jolt. EX: slinky
Secondary wave- Shear motion (side to side). More destructive than P-waves.
What is a surface wave?
they only travel along the surface, NOT through the Earth
What waves are the slowest and most destructive?
Love waves (back and fourth) Rayleigh waves (ripples on a pond)
What is a Seismograph?
They record the ground shaking of the earthquake waves on a seismograph
How do we locate earthquakes?
- Use the time interval between p-wave and s-wave.
- Arrival time of p-waves and s-waves indicate distance, NOT direction of the Earthquake.
- Wave arrival time needed from at least 3 stations to pinpoint location of earthquake use for triangulation of epicenter.
Modified Mercalli Intensity Scale
Reflects the subjective observations of how strongly people feel shaking and the severity of damage.
- Strongest happening: near the epicenter OR where ground conditions favor strong ground shaking.
What earthquake was the first one to be seen on live television?
Loma Prieta Earthquake, 1989 (6.9) at the world series game
